Removal of hexavalent chromium

Overview

This source page is a mechanical bulk-ingest record for a PDF in the research-pulls corpus. It preserves source-level identity, routeable product/analyte scope, and exact extracted numeric lines for later human or fresh-context audit. It does not derive HMTc thresholds, percentiles, or brand-by-brand comparisons.

Key numbers

The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:

• single bacterial isolates, there remains a significant gap in our contained low dissolved oxygen (≤1.4 mg/L), and had total Cr
• understanding of Cr(VI) removal by mixed microbial concentrations of 45 ± 1 μg L-1 (Supplementary Table S1). A
• transformation dynamics. Microbial mats, in particular, play a acid (TCA) (100% w/v) was prepared by adding 11 g (>99% purity)
• environment, by leveraging the physiological versatility of their Karnovsky’s fixative buffer was prepared by mixing 10 mL of 5%
• aerobic and anaerobic microorganisms (Abed et al., 2002; Bender, paraformaldehyde, 10 mL of 50% glutaraldehyde, and sodium-
• occur under anaerobic conditions. Indeed, there is a notable pure nitrogen gas (99.9% purity) for 15 min, after sealing the bottles
• procedure created strictly anaerobic conditions throughout the formaldehyde (36.5%) and TCA (20% w/v), and quantified by
• Since all three mats demonstrated similar Cr(VI) removal at the biomass was subjected to digestion using 1% HNO3 before analysis.
• carbazide (0.03%) under acidic conditions at 540 nm according to of Cr(VI) using 1 mL of CFE was first determined, and was found to
• ethanol (100%, 90%, 70% and 50%). The sample was then dried at incorporated on the forward primer (Klindworth et al., 2013).
• mapping by SEM-EDX was performed for Cr. To obtain for their intensity and size by electrophoresis on 2% agarose gel. PCR
• Mat A, B, and C removed ≥96 ± 2% of 1 mg L-1 of Cr(VI) after
• 4.7 ± 0.15 mg L-1 (corresponding to 94% ± 3% of initial
• (A) Removal of 1 mg L-1 Cr(VI) by three microbial mats (A, B and C) concentration) and 13.9 ± 0.45 mg L-1 (corresponding to 93% ±
• 3% of initial concentration) of Cr(VI) when incubated at the
• anaerobic conditions. Each incubation was done in triplicates (n = 3). respectively (Figure 1B). Most of Cr(VI) removal occurred in the
• Cr(VI), approximately 13 ± 0.6 mg L-1 (ca. 65% ± 3% of initial
• bases. Further steps involved denoising, chimera elimination, and approximately 43% ± 5% of the initial concentration (21 ±
• OTU clustering at 97% similarity. Taxonomic assignments were 2.5 mg L-1) of Cr(VI) was already removed after 15 days of
• occurred specifically at 400, 1,019, 1,432, 1,657, 2,943, 2,950, 3,276, 31 mg L-1 at 100 mg L-1 incubation (Table 1).
• TABLE 1 Removal of Cr(VI) at different concentrations (mg L-1) by a microbial mat through bioreduction to Cr(III) and biosorption on cell surface.
• 3.3 Bioreduction of Cr(VI) under anaerobic supernatant (23.2% of initial concentration), but only 0.95 mg L-1
• conditions (9.5%) in the mat (Figure 4B; Table 1). At higher Cr(VI)
• and in the mat after acid digestion (Figure 4; Table 1). At low Cr(VI) cases. In the mat, ca. 29 and 75 mg L-1 of the total Cr was detected at
• Cr(III) in the supernatant than in the mat (Figures 4A,B). At 1 mg L- in the form of Cr(III) (Figures 4C,D; Table 1). This corresponds to
• Cr(VI), 0.44 mg L-1 was converted to Cr(III) in the supernatant ca. 58% and 75% Cr(VI) reduction to Cr(III), respectively. Overall,
• (44% of initial concentration), whereas only 0.22 mg L-1 (22% of the total reduction of Cr(VI) to Cr(III) by Mat A increased with
• initial concentration) was reduced in the mat (Figure 4A; Table 1). increasing concentration from 0.66 mg L-1 when the mat was
• 100 mg L-1 of Cr(VI) under anaerobic conditions (Table 1). The by nOTU and Chao, decreased significantly after exposure of the
• protein. CFE could successfully remove 80% of 1 mg L-1 of Cr(VI) MiSeq analysis of the Cr(VI)-free mats revealed that
• 25%, 18% and 14% of the total sequences, respectively (Figure 6A).
• Proteobacteria, Bacilli, Phycisphaerae, Chloroflexia, Actinobacteria, proteobacteria and Actinobacteria were also detected at ≤13%
• Fusibacter, Desulfomaculum, Bacillus, Paenibacillus, and increased to make up between 22% and 48% of total sequences in
• change in the bacterial community composition, leading to the group reached between 14% and 51% of total sequences in each
• the different mat samples are the same as in Figure 5. (B) A heatmap showing the relative abundance (%) of the most dominant OTUs detected after
• these samples reached between 30% and 36%, each of total exhibited negative correlations with Phycisphaerae (r = −0.52, p =
• decreased to reach ≤9% of total sequences. Actinobacteria made up (r = −0.53, p = 0.02). Phycisphaerae correlated positively with
• to 25% of total sequences in only one sample incubated at 15 mg L-1 Deltaproteobacteria (r = 0.58, p = 0.01) and Planctomycetia (r =
• Cr(VI), and 20% in another incubated at 50 mg L-1 Cr(VI) 0.68, p = 0.001). Cr(VI) concentration was positively correlated with
• a relative abundance of 14% of total sequences, other groups such as 4 Discussion
• abundance between 12% and 17%. microbial mats
• ranging from 1 to 100 mg L-1. The ability of Mat A to remove 78% of cyanobacterial mat have demonstrated the ability to remove Cr(VI)

Methods (brief)

• Khan MTA, Al-Siyabi SS, Ali HE and Abed RMM removal of Cr(VI) by a microbial mat collected from a chromite mining site under
• microorganisms for Cr(VI) removal is associated with many samples and three different types of microbial mats (termed
• advantages including: 1) the lower energy requirement, especially hereafter as Mat A, B, and C). The intact mats were collected in
• simultaneous treatment of other pollutants such as nitrates and sampled mats are provided in Supplementary Figure S1. The
• aerobic conditions (Abed et al., 2020). Additionally, aerobic The ability of the mixed communities in the three sampled mats
• Since all three mats demonstrated similar Cr(VI) removal at the biomass was subjected to digestion using 1% HNO3 before analysis.
• samples of Mat A were then incubated under the same conditions as (ICP-OES) (Optima 8000DV, Perkin Elmer, United States), whereas
• intervals in all these incubations. Samples were collected and determined by ICP-OES (Khan et al., 2024).
• 100 mg L-1 Cr(VI) under the same anaerobic conditions described mat samples (i.e., Mat A, B and C), analyzed immediately after
• above. The bottles were incubated for 30 days. The site water with sampling, and on the incubated Mat A samples with and without
• Biosorption: To confirm the biosorption of Cr(VI) on the surface triplicate mat samples using the skim milk method (Volossiouk
• United States) analysis was performed. The mat sample was United States) to carry out paired-end Illumina MiSeq
• ethanol (100%, 90%, 70% and 50%). The sample was then dried at incorporated on the forward primer (Klindworth et al., 2013).
• alterations and the functional groups involved in biosorption, pooled samples were then used to construct a DNA library in
• collected by centrifugation at 5,000 rpm for 10 min, dried at 80 °C for which included merging sequences, removing barcodes, and
• collected from Nakhal quarry sumps after incubation in the dark under
• were calculated based on equal subsets of sequences for all samples (to conditions
• the lowest number of sequences found in any sample), using an

Implications

This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.

Wiki pages this source may touch

• Fish — marine, non-predatory (sardines, anchovies, salmon, cod)
• Aluminum
• Chromium

Verification notes

• Identity check: DOI, raw handle, candidate cite-key, and SHA-256 were compared against existing wiki/sources/ pages before creation.
• Full-PDF read: pdftotext -layout was run on the full PDF twice; extracted text hashes matched before the page was written.
• Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
• Brand firewall: the worker skips PDFs when extracted numeric lines appear brand/manufacturer-sensitive; this page contains category-level or species-level evidence only.
• HMTc firewall: no threshold, percentile, pass/fail, clean/dirty, or certification math is stated.

Update history

The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.